An AlGaAs/InGaAs pseudomorphic HEMT modulator driver IC with low power dissipation for 10 Gb/s optical transmission systems

An optical modulator driver IC has been developed for 10 Gb/s optical communication systems. In order to realize both high frequency operation and low power dissipation, 0.2-/spl mu/m T-shaped gate AlGaAs/InGaAs pseudomorphic HEMTs, which give large transconductance, g/sub m/, of 610 mS/mm and high cut-off frequency, f/sub T/, of 67.5 GHz, have been employed. In addition, by using a current mirror circuit with cascode configuration as high impedance current source, power dissipation of 1.1 W is achieved at a 10 Gb/s NRZ signal output with 3 V/sub p-p/. This dissipation is the lowest value ever reported. As an additional function, the output voltage swing can be controlled from 2 to 3.3 V/sub p-p/ by the current mirror circuit in order to adjust the duty factor of optical output signal through an optical modulator.